11:00 〜 13:00
[PPS08-P01] 木星によって励起された微惑星によるコンドリュール生成率と集積率の解明
キーワード：隕石、コンドリュール
Chondrules are silicate materials contained in ordinary chondrites that fall to the Earth in large numbers, and account for nearly 80% of the volume of meteorites. Its shape is spherical, and its diameter is about 0.1 to 1 mm.
The chondrules were formed when the silicates were heated, melted, and cooled rapidly. The chondrules were then incorporated into the meteorite parent body, and it is believed that chondrules were formed by collisions between asteroids in the asteroid belt.
From the dating of meteorites, it is known that chondrules were formed only a few million years after the formation of the solar system. In other words, the formation of the solar system is thought to have been accompanied by solid-melting events.
We focus on the planetesimal collisional heating model, which is one of the main chondrule formation scenarios currently considered.
Nagasawa et al. 2019 calculates the orbital evolution of planetesimal after the formation of Jupiter, but the efficiency of chondrule formation is discussed. The numerical results indicate that the period during which chondrules can form is several million years after Jupiter formation. However, the amount of chondrule formation and the amount of accumulation by planetesimal after chondrule formation have not been discussed.
In this study, we calculate the amount of chondrule formation and accumulation by planetesimal excited by orbital resonance after the formation of Jupiter based on the planetesimal impact heating model.
We consider that a chondrule-accumulating planetesimal must satisfy the following three conditions simultaneously. (1) the chondrule layer must be more than 20 km, (2) the present asteroid belt contains planetesimal in 2 to 3 au, and (3) the average eccentricity of planetesimal in the asteroid belt is about 0.1.
First, the number of collisions between planetesimal in the protoplanetary disk is calculated, and then the amount of chondrules produced and accumulated on the planetesimal are determined. As for the chondrule production mass, the volume of chondrules produced by one collision between two planetesimal has been clarified by Sirono and Turrini (in preparation), and the chondrule production mass is calculated using the results of Sirono and Turrini (in preparation).
In the protoplanetary disk, there are many planetesimals of various sizes. In this calculation, for the sake of simplicity, 10 large planetesimal with a radius of 500 km are equally distributed in 2 to 3 AU, and 90 small planetesimal in 2 to 5 au.
The radii of the smaller planetesimal were calculated with the parameters 1 km, 10 km, and 100 km. The dissipation time of the gas disk is also set to 50,000, 500,000, and 5,000,000 years.
The formation and accumulation of chondrules depend strongly on the excitation of the planetesimal because the excitation of the planetesimal is changed by changing the radius and the gas dissipation time. In this calculation, we adopt the radius of the planetesimal and the gas dissipation time as parameters.
As a result of nine different calculations with different planetesimal and gas dissipation times, it is found that the larger the radius of the planetesimal, the better it is to produce chondrules, and the longer the dissipation time, the better it is to accumulate them.
On the other hand, in order to satisfy the current eccentricity and spatial distributions of the asteroid belt, the gas dissipation time should be shorter, which leads to a contradiction between the three conditions.
Therefore, at the end of the calculation (5 million years), there will be no solution that satisfies the three conditions. However, there is a case where the three conditions are satisfied at around 1 million years only when the gas dissipation time is 500,000 years and the radius of the planetesimal is 10 km or 100 km. In both cases, the conditions are no longer satisfied after 1 million years due to gas drag (figure).
These results indicate that the gas dissipation is an important parameter to determine whether the conditions are satisfied or not.
Nagasawa et al. (2000) found that the secular resonance point moves from the inside to the outside when the gas is dissipated from the inside.
These results indicate that the gas dissipation is an important parameter to determine whether the conditions are satisfied or not.
Nagasawa et al. (2000) found that the secular resonance point moves from the inside to the outside when the gas is dissipated from the inside.
In the future, we would like to investigate how the results of this calculation are changed by changing the method of gas dissipation and the movement of the secular resonance point.
The chondrules were formed when the silicates were heated, melted, and cooled rapidly. The chondrules were then incorporated into the meteorite parent body, and it is believed that chondrules were formed by collisions between asteroids in the asteroid belt.
From the dating of meteorites, it is known that chondrules were formed only a few million years after the formation of the solar system. In other words, the formation of the solar system is thought to have been accompanied by solid-melting events.
We focus on the planetesimal collisional heating model, which is one of the main chondrule formation scenarios currently considered.
Nagasawa et al. 2019 calculates the orbital evolution of planetesimal after the formation of Jupiter, but the efficiency of chondrule formation is discussed. The numerical results indicate that the period during which chondrules can form is several million years after Jupiter formation. However, the amount of chondrule formation and the amount of accumulation by planetesimal after chondrule formation have not been discussed.
In this study, we calculate the amount of chondrule formation and accumulation by planetesimal excited by orbital resonance after the formation of Jupiter based on the planetesimal impact heating model.
We consider that a chondrule-accumulating planetesimal must satisfy the following three conditions simultaneously. (1) the chondrule layer must be more than 20 km, (2) the present asteroid belt contains planetesimal in 2 to 3 au, and (3) the average eccentricity of planetesimal in the asteroid belt is about 0.1.
First, the number of collisions between planetesimal in the protoplanetary disk is calculated, and then the amount of chondrules produced and accumulated on the planetesimal are determined. As for the chondrule production mass, the volume of chondrules produced by one collision between two planetesimal has been clarified by Sirono and Turrini (in preparation), and the chondrule production mass is calculated using the results of Sirono and Turrini (in preparation).
In the protoplanetary disk, there are many planetesimals of various sizes. In this calculation, for the sake of simplicity, 10 large planetesimal with a radius of 500 km are equally distributed in 2 to 3 AU, and 90 small planetesimal in 2 to 5 au.
The radii of the smaller planetesimal were calculated with the parameters 1 km, 10 km, and 100 km. The dissipation time of the gas disk is also set to 50,000, 500,000, and 5,000,000 years.
The formation and accumulation of chondrules depend strongly on the excitation of the planetesimal because the excitation of the planetesimal is changed by changing the radius and the gas dissipation time. In this calculation, we adopt the radius of the planetesimal and the gas dissipation time as parameters.
As a result of nine different calculations with different planetesimal and gas dissipation times, it is found that the larger the radius of the planetesimal, the better it is to produce chondrules, and the longer the dissipation time, the better it is to accumulate them.
On the other hand, in order to satisfy the current eccentricity and spatial distributions of the asteroid belt, the gas dissipation time should be shorter, which leads to a contradiction between the three conditions.
Therefore, at the end of the calculation (5 million years), there will be no solution that satisfies the three conditions. However, there is a case where the three conditions are satisfied at around 1 million years only when the gas dissipation time is 500,000 years and the radius of the planetesimal is 10 km or 100 km. In both cases, the conditions are no longer satisfied after 1 million years due to gas drag (figure).
These results indicate that the gas dissipation is an important parameter to determine whether the conditions are satisfied or not.
Nagasawa et al. (2000) found that the secular resonance point moves from the inside to the outside when the gas is dissipated from the inside.
These results indicate that the gas dissipation is an important parameter to determine whether the conditions are satisfied or not.
Nagasawa et al. (2000) found that the secular resonance point moves from the inside to the outside when the gas is dissipated from the inside.
In the future, we would like to investigate how the results of this calculation are changed by changing the method of gas dissipation and the movement of the secular resonance point.